The following disclosure is based on German Utility Model Application No. 200 19 879.3, filed on Nov. 23, 2000, which is incorporated into this application by reference.
The invention relates to a face seal device having a supplemental mass, for use with components rotating at a high rotational speed.
The invention relates, in particular, to a face seal device which is not only suitable for use at high rotational speeds but which is especially suitable likewise for sealing high pressures. In applications of this type, it is preferred that ceramic materials be used for the rotary face seal ring because of the high wear-resistance properties of these materials. At high rotational speeds, despite the fundamentally high resistance of ceramic materials such as silicon carbide (SiC) or sintered materials such as tungsten carbide (WC) to thermal distortions, and despite of lack of direct contact between the face seal rings, the face seal ring may experience a heating due to friction with the gaseous or liquid medium in the sealing clearance (molecular friction) to such an extent as to lead to intolerable thermally induced distortions or deformations of the rotary face seal ring, whence the geometry of the sealing clearance could be adversely affected. In particular, the sealing clearance may open in the manner of a wedge (the formation of a so-called V-gap) thereby resulting in considerably increased leakages.
One object of the invention is to provide an improved face seal device suitable for high rotational speeds while having minimized leakage. A further, more particular object of the invention is to provide a face seal device in which detrimental effects in regard to the geometry of the sealing clearance between co-operating face seal rings caused by thermally induced distortions of a rotary face seal ring can be either entirely prevented or prevented to the best extent possible.
These and other objects are achieved in accordance with the present invention by a face seal device for use with components rotating at a high rotational speed. According to one formulation of the invention, such a face seal device includes a non-rotating face seal ring and a rotary face seal ring. The rotary face seal ring is mounted in a loose fit for common rotation with a rotating component and includes a sealing face which, in operation, is essentially radially aligned for cooperation with an opposite sealing face of the non-rotating face seal ring. A mass-contributing element, preferably relatively heavy, is arranged to rotate in common with the rotating component and engages a portion of the rotary face seal ring. The center of gravity of the mass-contributing element is axially spaced from that of the rotary face seal ring, whereby a torque directed towards the non-rotating face seal ring is exerted to the rotary face seal ring in correspondence with the centrifugal forces arising due to the mass-contributing element and the spacing between the centers of gravity.
A thermally induced deformation of the rotary face seal ring is thereby effectively countered and a compensating effect for a change in the geometry of the sealing clearance caused by such a deformation is thus obtained. As a result, the desired geometry of the sealing clearance will be maintained even when the rotary face seal ring is used at high to very high rotational speeds.
The preferred rectangular form of the cross-sectional configuration of the rotary face seal ring can be retained with the invention. This is beneficial, since this form has proved to be advantageous both in regard to the operational behavior, production and mounting of the face seal ring as well as to the replacement of worn face seal rings. In order to ensure a uniform distribution of the centrifugal forces around the periphery of the rotary face seal ring, it is preferred, according to an embodiment of the invention, that the mass-contributing element be composed of a plurality of peripherally distributed individual masses, in which the individual masses may be mutually discrete or connected to one another in articulated manner.